This invention relates to a thermoplastics extrusion plastometer cleaning device, especially, a device for cleaning automatically the cylinder, piston and die of the extrusion plastometer for testing the plasticity of the thermoplastics.
The extrusion plastometer tests the plasticity of the thermoplastics. The test is carried out by extruding melted thermoplastics through a die of a stipulated length and bore at a stipulated temperature and under stipulated pressure to measure the extrusion speed. There are two procedures for the test; Procedure A and Procedure B (stipulated by JIS). In procedure A, a mass which is extruded in a unit hour is manually cut off to be measured. In Procedure B, a time in which a unit of mass is extruded is measured. The plasticity of the melted polymer materials, such as thermoplastics, is related with the shearing speed thereof. The result of the plasticity test provides one index for their forming. Thus the plasticity test is important. This invention is usable in cleaning the cylinders, pistons and dies used in both of the above described Procedures A and B.
The procedures of the plasticity test on the thermoplastics are stipulated in detail in JISK7210 1976 and are not referred to herein. The portion of the procedures which is related with this invention and pertains to the manual measurement will be briefed.
The prior art manually operated test device has an electric furnace and a stipulated quantity of a test specimen is placed in a metal cylinder which has been controlled to have a measurement temperature by the electric furnace and melted. A weight of a stipulated mass is mounted on a piston inserted into the cylinder to extrude the melted specimen downward through a die of small bore arranged in the bottom part of the cylinder. When the test is completed in accordance with Procedure A or B, a manual force is applied to the weight to force the specimen residue in the cylinder down out of the cylinder through a die. Before a test is started anew, the part of the specimen for a last test sticking to the cylinder, piston and die has to be perfectly removed therefrom. Otherwise correct measurement cannot be made. Conventionally the cylinder has been cleaned by sliding a cylinder cleaning rod with soft cloth wound thereon. The cleaning was carried out by sliding the cylinder cleaning rod manually twice to three times in the cylinder.
And the piston cleaning has been carried out by wiping off the residual specimen on the piston surface with a soft cloth by an examiner.
Moreover, the die cleaning was carried out with a brass or wooden rod by taking out the die from the bottom of the cylinder after the cylinder cleaning.
The cleaning described above must be carried out essentially before a test. Without the cleaning undesirable specimen residue of a last test affects the following test. The cleaning has to be carried out at high temperatures since the cylinder is heated up to a high temperature as high as 125.degree. to 300.degree. C., which varies depending on specimens. Otherwise the specimen residue is cured, and it becomes difficult to remove it.
The conventional cleaning of the cylinder has been carried out manually since no suitable automatic cleaning means has been available. Such manual cleaning has been accompanied by the following disadvantages, safety problems due to the cleaning of the cylinder under a high temperature, increased costs due to the manual cleaning; lower precision of the measurement due to a nonuniform cleaning of the cylinder. Because of these disadvantages, an automatic cleaning of the cylinder has been earnestly expected.